Regulation of mouse kidney tubular epithelial cell-specific expression of core 2 GlcNAc transferase.

A mouse gene, Gsl5, controls the expression of Galbeta1-4(Fucalpha1-3)GlcNAcbeta1-6(Galbeta1-3)Gb4Cer and its precursor glycolipids in the kidney by regulating transcription of beta-1,6-GlcNAc transferase. Here we report that Gsl5 controls the expression of the core 2 structure [GlcNAcbeta1-6(Galbeta1-3)GalNAcalpha1-Ser/Thr] of glycoproteins as well as the glycolipid, GlcNAcbeta1-6(Galbeta1-3)GalNAcbeta1-3Galalpha1-4Galbeta1-4Glcbeta1-ceramide. Immunohistochemical studies using an anti-(core 2-Lex) monoclonal antibody demonstrated that lysosome-like vesicles of proximal tubule cells were clearly stained in a Gsl5 wild type mouse, but not in a Gsl5 mutant strain of mice. Western blotting of microsomal fractions of kidney tissue with the same antibody confirmed the histological findings. In situ hybridization with an antisense probe to the kidney-specific mRNA demonstrated that the mRNA is localized at proximal tubule-cells in the cortex adjacent to the medulla, but not detected in glomeruli nor in collecting duct cells in the medulla. The results obtained by immunohistological staining and in situ hybridyzation are compatible and lead to the conclusion that the kidney specific mRNA is expressed in a proximal tubular cell specific manner and produces core 2 GlcNAc transferase responsible for the production of glycoproteins localized at vesicles in the proximal tubular cells. Glycosylation regulated by Gsl5 gene may modify functions of membrane glycoproteins in proximal tubular cells.